This document provides an introduction to mycology, the study of fungi. It discusses the history of fungi being recognized as pathogens and outlines the key characteristics of fungi such as cell walls containing chitin. Fungi can be classified based on cell morphology into yeasts, molds, and dimorphic fungi. They can also be classified based on sexual reproduction into four classes. Common fungal infections like dermatophytosis and opportunistic infections are described. The document concludes by noting some useful properties of fungi such as food production and antibiotic production.

1. Introduction to
Mycology
Dr. Dinesh Jain
Assistant Professor
Deptt. of Microbiology
SMS MC Jaipur

2. HISTORY
 Fungi were recognized as causative agents of
human disease earlier than bacteria (1839)
 They received scanty importance due to their
benign nature of the diseases caused.
 Fungal infections are however very common,
serious and even fatal.
 Modern advances in treatment such as
antibiotics, steroids& immunosuppressive drugs
have led to an increase in opportunistic
pathogenic infections.

3. Introduction
 Fungi are eukaryotic protista; differ from
bacteria and other prokaryotes.
1. Cell walls containing chitin (rigidity & support),
mannan & other polysaccharides
2. Cytoplasmic membrane contains ergosterols
3. Possess true nuclei with nuclear membrane &
paired chromosomes.
4. Divide asexually, sexually or by both
5. Unicellular or multicellular

4. Introduction
 Simplest fungus :- Unicellular budding
yeast
 Hypha :- Elongation of apical cell
produces a tubular, thread like structure
called hypha
 Mycelium :- Tangled mass of hyphae is
called mycelium. Fungi producing
mycelia are called molds or filamentous
fungi.
 Hyphae may be septate or non-septate

5. Classification
 Fungi can be classified
 Depending on cell morphology :4
types
 Based on sexual spore formation: 4
classes

6. CLASSIFICATION
 Depending on cell morphology
1. Yeasts
2. Yeast like fungi
3. Molds
4. Dimorphic fungi

7. 1. Yeasts
 Unicellular fungi which
reproduce by budding
 On culture - produce
smooth, creamy colonies
e. g Cryptococcus
neoformans (capsulated
yeast)

8. 2. Yeast like fungi
 Grow partly as yeasts and partly as
elongated cells resembling hyphae which
are called pseudohyphae.
 e.g. Candida albicans

9. 3. Molds/ Filamentous fungi
 Form true mycelia &
reproduce by formation
of different types of
spores.
 Vegetative/ aerial
hyphae
e.g. Rhizopus, mucor

10. 4. Dimorphic fungi
 Occur in 2 forms
Molds (Filaments) – 25C (soil)
Yeasts – 37C (in host tissue)
Most fungi causing systemic infections
are dimorphic:
 Histoplasma capsulatum
 Blastomyces dermatidis
 Paracoccidioides brasiliensis
 Coccidioides immitis
 Penicillium marneffei
 Sporothrix schenkii

11. Systematic classification
 Based on sexual spore formation: 4
classes
1. Zygomycetes
2. Ascomycetes reproduce sexually
3. Basidiomycetes
4. Deuteromycetes (fungi imperfectii)

12. 1. Zygomycetes
 Lower fungi
 Broad, nonseptate hyphae
 Asexual spores -
Sporangiospores: present
within a swollen sac- like
structure called
Sporangium

13. 1. Zygomycetes
 Sexual spores -
Zygospore: a
resting, thick walled
cell in between
hyphae
e.g. Rhizopus,
Mucor, Absidia

14. 2. Ascomycetes
 Includes both yeasts & filamentous fungi
 Narrow, septate hyphae
 Asexual spores are called conidia borne on conidiophore

15. 2. Ascomycetes
 Sexual spores called
ascospores are present
within a sac like structure
called Ascus.
 Several asci may be seen
within a fruiting body as seen
in Penicillium, Aspergillus
 Each ascus has 4 to 8
ascospores.

16. 3. Basidiomycetes
 Sexual fusion results in the formation of a
club shaped organ called base or basidium
which bear spores called basidiospores e.g.
trichosporon,malassezia

17. 4. Deuteromycetes
or Fungi imperfectii
 Group of fungi whose sexual phases are
not identified.
 Grow as molds as well as yeasts.
 Asexual stage – conidia
e.g. Candida, Cryptococcus

18. Vegetative Structures of Fungi
 Formed by the vegetative mycelia
(modification of single vegetative cells or
hyphae)
 Have no reproductive value
 Important in the differentiation/
identification of clinically significant fungi.

19. Spiral hyphae in
T.Mentagrophytes

20. Vegetative Structures of
Fungi
 Arthrospores –
formed by
segmentation &
condensation of
hyphae
 Chlamydospores –
thick walled resting
spores
e.g. C.albicans

21. Reproduction in fungi
 Sexual - formation of zygospores,
ascospores or basidiospores
 Asexual reproduction – budding or fission
 Asexual spores are formed on or in
specialized structures.
 Vary in size, shape & colour but these
characteristics are constant for a particular
species.

22. Reproduction in fungi
 Micro conidia -
Small, single
celled
 Macro conidia –
Large, single or
many celled

23. Fungal Infections/ Mycoses
 Superficial mycoses:
 2 types: surface and cutaneous mycoses
 Skin, hair & nails.
 Mild but chronic disease
 Deep mycoses:
 2 types: subcutaneous & systemic mycoses
 Caused by soil saprophytes
 Infection is accidental
 Range from a symptomatic infection to fatal disease

24. Superficial: Surface mycoses
 Live exclusively on dead surfaces of
skin and its appendages
 No contact with living tissue, hence no
inflammatory response
1. Tinea versicolor
2. Tinea nigra
3. Piedra

25. Superficial: Cutaneous mycoses
 Cornified layer of skin & its appendages
 Contact with living tissue, hence
inflammatory & allergic responses seen
1. Dermatophytes – skin, hair & nails
2. 3 genera - Trichophyton
Microsporum
Epidermophyton

26. Deep mycoses
Subcutaneous mycoses
1. Mycotic Mycetoma
2. Chromoblastomycoses
3. Sporotrichosis
4. Rhinosporidiosis
5. Subcutaneous
phycomycoses
Systemic mycoses
1. Cryptococcoses
2. Blastomycosis
3. Paracoccidiomycoses
4. Coccidioidomycoses
5. Histoplasmoses

27. Candidiasis
 Caused by candida sps, forms a bridge
between superficial & deep mycoses as
it can cause cutaneous as well as
systemic infections
 Can also cause opportunistic infections

28. Opportunistic infections
 Pts with debilitating disease, altered
physiological state
 Mainly caused by fungi which are common lab
contaminant on culture media
 Aspergillus
 Pencillium
 Mucor
 Rhizopus
 Produce serious & fatal infections

29. Useful Properties of Fungi
Source of food
e.g. mushrooms
Fermentation - Production of
alcohol, bread
e.g. Sacchromyces spps
Antibiotic production
e.g. Penicillin from
Penicillium notatum

30. Useful Properties of Fungi
Ergot from Claviceps
purpurea, used to induce
uterine contractions
Vaccines for Hepatitis B –
Sacchromyces cerevisiae